Abstract

Background: Primary hyperaldosteronism is more frequent among subjects with essential hypertension than previously thought. The prevalence, according to local and international evidence could fluctuate between 9 and 10%. Aim: To investigate if subjects with essential hypertension have different aldosterone and renin plasma levels than normotensive subjects. Patients and methods: One hundred twenty five subjects with essential hypertension, not receiving medications for a least two weeks prior to the study and 168 age and sex matched normotensive controls were studied. Blood was drawn between 9 and 10 AM during a sodium free diet to determine plasma aldosterone, plasma renin activity and potassium. Results: Plasma aldosterone was higher in hypertensive subjects than controls (11.6 +/- 7.6 and 9.9 +/- 5.1 ng/dl respectively; p = 0.04). Plasma renin activity was lower in hypertensives than controls (1.42 +/- 1.28 and 1.88 +/- 1.39 ng/ml/h respectively; p < 0.001). Thus, plasma aldosterone/plasma renin activity ratio was higher in hypertensives (13.8 +/- 13.5 and 8.3 +/- 7.8; p < 0.001), A pathological ratio was defined as over 25, corresponding to the mean plus two standard deviations of the control group. Primary hyperaldosteronism was found in 5/125 hypertensives (4%) and 1/168 normotensive subject (0.6%). None had hypokalemia. Conclusions: Subjects with essential hypertension have higher plasma aldosterone and lower plasma renin activity than normal controls. A plasma aldosterone/plasma renin activity over 25 was defined as abnormal.